1. Field of the Invention
The present invention relates to a humidifier for humidifying a dry fluid, using moisture in a humidified fluid.
2. Description of the Related Art
As a fuel cell for a fuel cell electric vehicle (FCEV) is generally adopted, for example, a PEM (Proton Exchange Membrane) type using a solid polymer as an electrolyte membrane because of a small size and light weight, high efficiency, and high power output thereof. An ion exchange membrane such as a fluorocarbon resin group cited as one of solid polymers functions as a proton conductive electrolyte membrane in a water containing state; however, in a dry state its proton conductivity lowers and it causes a lowering of a power output. Therefore, a fuel cell system equipped with this kind of a fuel cell is designed to humidify reaction gases (anode gas and cathode gas) supplied to an anode and cathode of the fuel cell by a humidifier so that an electrolyte membrane can maintain proper humidity.
Although a humidifier for humidifying the reaction gases is variously proposed, the humidifier is proposed which uses a hollow fiber membrane and humidifies the reaction gases by an off-gas discharged from a fuel cell because of no necessity of a water supply from outside and power, its comparatively simple structure, and the like (for example, see paragraph 0020 and FIGS. 3 and 4 in Japanese Patent Laid-Open Publication No. 2003-156238).
However, in the conventional humidifier, if the fuel cell system stops and the humidifier is cooled, the reaction gases humidified are cooled, thereby condensation water is produced, and the water accumulates in the vicinity of an outlet of the reaction gases of the humidifier. Therefore, if the fuel cell system is started in this state, the condensation water accumulated in the vicinity of the outlet flows toward the fuel cell provided at a downstream, as a result, a reaction face within the fuel cell, that is, an electrode face covering the outside of the electrolyte membrane is excessively covered by the condensation water, thereby it becomes difficult for the reaction gases to be supplied to the electrode face, and a power generation efficiency of the fuel cell lowers.
Consequently, a humidifier is strongly requested that can prevent condensation water accumulated in the vicinity of an outlet of the humidifier from flowing toward a fuel cell at start of a fuel cell system.